I have a Carrier Infinity 17 model 38YDB heat pump with a Carrier Infinity 96 2 stage, variable speed furnace as auxillary heat. When the outside temperature is 43 degrees and inside temp. of house is 69 deg. with a thermastat setting of 69deg., the heat pump is running almost constantly,(maybe off for 1/2 hour during an 8 hr. period). The temp. of air coming from the ducts is between 65 and 67 degrees. Seems to me kinda like a dog chasing its tail. Ductwork is uninsulated in the basement. Carrier infinity thermostat furnace lockout set at >35 deg. with heat pump lockout of <20 deg.

What temp. should I be getting from duct vent with this heat pump? Any ideas of why the temp. of air is low?

Both units are less than a month old and company installer says this is normal operation. Is this really normal? Doesn't seem too energy efficient in my terms of thinking, course my thinking terms are sometimes wacky at times.

Thanks for your inputs

 

scruffy

No this is not normal. I am assuming your dual fuel system was sized correctly. Is HP compressor running in low stage or high stage? You should be receiving a supply temp easily in the 90s and anyone who says otherwise is not being truthful. Your HP is running all the time because of these low supply temps. The reason why could be an improperly charged system. I am not certain I understand your lockout settings. Pls elaborate.

I would ask installing dealer to come back out to house and check set-up and watch operation for about an hour at outside temps around 40 deg fah. Ask him to bring a digital thermometer and check the readings at various supply vents. You should verify these readings. I would document in writing what you describe and give him a dated copy. Don't let dealer put you off for a premium system like yours. You deserve better.

My Opinion.

 

Thanks TigerDune. The heat pump is running in low stage for most of the time, only in high stage for a very little time. The lockout temps I described are:
The heat pump won't come on if outside temp is 20 degrees or lower and the furnace won't come on if the outside temp is 35 degrees or warmer. I will take your advice, I'll record date and temps of air from vents as well as outside temp and give the installer a call again to come check out system.

Thanks again,
scruffy

 

SCRUFFY,

Besides your issue regarding suppy temps, I don't like what you call lockout settings. I am familiar with dual fuel operations. For instance in a dual fuel system, I do like the restrictive set-up for heat pump operation vs gas furnace operation. You the homeowner is in control. This temperature setting should be based on your balance point-the outside temperature at which your heat pump can no longer maintain your inside thermostat setting in normal operation and has to call for auxillary heat. In a dual fuel system, the auxilliary heat is your gas furnace-rather than heat pump with strip heat. As an example, let's say your balance point has been calculated at 27 degrees outside temp with an inside thermostat setting at 70 deg fah. To give a little cushion, I would set the outside thermostat at 30 deg to switch back and forth between heat pump and gas furnace operation. It seems you have two lockout settings that really are in conflict.

Post back and let us know what your dealer says about your heat pump operation.

Good LucK!

 

Finally got heat pump working. The dealer/installer replaced the compressor. The supply temp on high heat pump operation was then in high 80's while in the low heat pump operation unchanged. He then replaced the expansion valve and suction line, suction line had a kink in it. Now heat pump would supply heat in low 90's on low heat pump and high 90's in high heat pump operation when outside temp. was at 35.

Now after a couple of weeks with the same outside temp, the heat pump operating in low will only supply about 87deg. and on high will only put out about 91deg.

Any thoughts on why the supply temps have dropped? or should I be satisfied with the supply temps I am now getting?

Thank you in advance for any reply.
Scruffy

 

with all the work they did posable refrigerant leak I'd have them back out to check the system.

 

scruffy

I would not accept these supply temps since it appears they are drifting lower. It is generally a little difficult to charge a heat pump properly in cold weather. However, it can be done by experienced HVAC techs. They should have a chart to accomplish this. I suspect you either have an improperly charged system or a leak at the connection points. Get your dealer back out. Something is wrong.

My opinion.

 

How old is this system and did they give you a possible reason for compressor failure? Is your a-coil in the supply plenum? If it is, the heat pump must be locked out when the furnace comes on.